Grounding and testing device for electrical switchgear

ABSTRACT

A grounding and testing device for use in electrical switchgear having a stationary housing with two sets of primary supply sockets for feeder and busbar circuits respectively and a movable housing with two sets of primary supply plugs for connection to the sockets and connected to the contacts of switching apparatus in the movable housing, the device comprising a carrier, a set of primary supply extension plugs mounted on the carrier for engaging at one end thereof a set of the primary supply sockets and at the other end thereof a first set of the primary supply plugs, a set of primary supply contacts for engaging a second set of the primary supply plugs, ground contacts connected to the primary supply contacts, a first locking mechanism for locking the carrier in position on the movable housing, and a second locking mechanism for locking the carrier in position on the stationary housing.

United States Patent 3,869,587 Caton Mar.4, 1975 GROUNDING AND TESTING DEVICE ELECTRICAL SWITCHGEAR Primary E.raminer-Robert K. Schaefer Assistant E.raminerJohn W. Redman Attorney, Agent, or- FirmStevens, Davis, Miller & Mosher [5 7] ABSTRACT A grounding and testing device for use in electrical switchgear having a stationary housing with two sets of primary supply sockets for feeder and busbar circuits respectively and a movable housing with two sets of primary supply plugs for connection to the sockets and connected to the contacts of switching apparatus in the movable housing, the device comprising a carrier, a set of primary supply extension plugs mounted on the carrier for engaging at one end thereof a set of the primary supply sockets and at the other end thereof a first set of the primary supply plugs a set of primary supply contacts for engaging a second set of the primary supply plugs, ground contacts connected to the primary supply contacts, a first locking mechanism for locking the carrier in position on the movable housing, and a second locking mechanism for locking the carrier in position on the stationary housing.

6 Claims, 6 Drawing Figures PATENTED 41975 sum 2 or g PATENTED 41975 sum 3 [IF 5 GROUNDING AND TESTING DEVICE FOR ELECTRICAL SWITCHGEAR This invention relates to a device for use in the grounding and testing of high voltage electrical switchgear.

In conventional high voltage switchgear the feeder circuit and busbar circuit are contained in a stationary housing, and switching means for connecting these two circuits, usually in conjunction with a circuit breaker, are contained in a movable housing. The stationary housing has two sets of primary supply sockets for the feeder and busbar circuits respectively and the movable housing has two sets of mating primary supply plugs connected to the contacts of the switching means. The primary supply plugs and sockets are connected when the movable housing is moved into an operative position relative to the stationary housing.

When maintenance of the switchgear or cables connected thereto is to be effected it is a requirement that the feeder circuits be grounded, and it can also be necessary to ground the busbar circuits. It is known to effect such grounding by a device which may be secured to the movable housing and which effectively provides extension of one set of the primary supply plugs for engagement with the set of sockets of either the feeder or the busbar circuits. The device also provides contacts for engaging the other set of primary supply plugs and connected to ground contacts on the movable and stationary housings. The ground contacts can thus be connected to the stationary supply sockets by closing the switching means in the movable housing. Such known grounding devices must be removed from the feeder or busbar circuits when test probes need to be inserted into the primary supply sockets associated with such circuits. These sockets can be somewhat inaccessible and the testing procedures can be somewhat hazardous.

According to the present invention we provide a grounding and testing device for use in electrical switchgear having a stationary housing with two sets of primary supply sockets for feeder and busbar circuits respectively and a movable housing with two'sets of primary supply plugs for connection to the sockets and connected to the contacts of switching means in the movable housing, the device comprising a carrier, a set of primary supply extension plugs mounted on the carrier for engaging at one end thereof a set of the primary supply sockets and at the other end thereof a first set of the primary supply plugs, a set of primary supply contacts for engaging a second set of the primary supply plugs, ground contacts connected to the primary supply contacts, first locking means for locking the carrier in position on the movable housing, and second locking means for locking the carrier in position on the stationary housing.

In use, the device is mounted on the movable housing with the primary supply extension plugs and the primary supply contacts engaging respective sets of the primary supply plugs on the movable housing and with the first locking means engaged. The movable housing is then advanced to the stationary housing to engage the primary supply extension plugs with the set of primary supply sockets to be grounded or tested. When in position grounding can be effected by closing the switching means in the movable housing so making a circuit from the primary supply sockets through the pri- 2 mary supply extension plugs, first set of primary supply plugs, switching means, second set of primary supply plugs, and primary supply contacts to the ground contacts.

If testing is to be effected the switching means is opened, the second locking means is engaged, the first locking means is disengaged and the movable housing is withdrawn. The device is thus left mounted and locked on the stationary housing and the primary supply extension plugs effectively form extensions from the primary supply sockets. The extension plugs can then be engaged by test probes and other equipment, so removing the problem of inaccessibility of the primary supply sockets.

Preferably the locking means are interconnected so that when one is fully engaged the other is fully disengaged.

The device may be designed for use in conjunction with any one of a number of different forms of movable and stationary housings.

In order that the invention may be better understood a specific embodiment of a device according to the invention will now be described in more detail, with ref erence to the accompanying drawings in which:

FIG. 1 is a side elevation of the device;

FIG. 2 is a plan of the device; and

FIGS. 3 to 6 are diagrams showing the modes of use of the device.

The device shown is specifically designed for use with three-phase high voltage electrical switchgear as described in our co-pending British application No. 12482/72. This comprises a stationary housing 1 (FIG. 3) housing three feeder circuits (not shown) connected to a first set of three horizontally aligned primary supply sockets such as 2 and three busbar circuits (not shown) connected to a second set of three horizontally aligned primary supply sockets such as 3. A movable housing 4 is mounted on wheels 5 for horizontal movement towards and away from the stationary housing. The movable housing has a first set of three horizontally aligned primary supply plugs such as 6, and a second set of three horizontally aligned primary supply plugs such as 7. The plugs are connected to contacts of switching means within the movable housing so that circuits may be made between vertically aligned plugs of each set. In normal operation of the switchgear the movable housing is positioned so that plugs 6, 7 engage sockets 2, 3 respectively.

As shown in FIGS. 1 and 2 the device comprises an insulating carrier 8 from which projects an insulating plate section 9 carrying three primary supply extension plugs 10 to 12 carrying cluster contacts 13 to 15 respectively at their forward ends and formed with sockets 16 to 18 respectively at their other ends. The section 9 also has shutter operating rods 19 mounted thereon. A further plate 20 is fixed to the carrier and supports three primary supply contacts in the form of star point contacts such as 21. These are connected to ground contacts in the form of conducting strips 22, 23 at each side of the device, each strip having two contacts 24 and 25.

Pivotally mounted between the strips 22, 23 is a shaft 26, at a level between the axes of extension plugs 10 to 12 and the axes of star point contacts 21. Each end of the shaft carries a lever 27 having a hook 28 formed on one arm thereof and a slot 29 formed in the other arm thereof. A handle30 is fixed to one of the levers 27.

'3 lnterlockmembers 31 are pivoted to each side of the carrier by pivotpins 32, each member having agroove 33 in which a pin 34 engages. Springs (not shown) bias the members 31 to the positions shown. At the ends opposite to the grooves 33 the levers have a section 35 shaped to lie above the space between the strips 22 and 23.

The plate 201, h2as pivoted thereto a cover 36 lying as shown in solid lineswhen thedevice is as shown in F IG. 1-, but taking up the broken line position relative to star point contacts 21 when the device is inverted. I Touse the device for grounding the feeder circuits in the stationary housing, the device is fitted to the movable housing as shown in FIG. 3, the switching means in the movable housing being open. When properly fitted the sockets 16 to l8-engage the first set of primary supply plugs 6 and the star point contacts 21 engage the second set of primary supply plugs 7. The ground contacts 25 engage contacts (not shown) fitted to the metal sides of the movable housing 4 to make grounding contact therewith. The handle 30 is then moved clockwise as shown in FIG. 1 to engage the slots 29 with pins 29a formed on opposite sides of the movable housing. The device is thus locked to the movable housing. To ground :the feeder circuits the movable housing is then advanced to the position shown in FIG. 4 where the cluster contacts 13 to 15 on the extension plugs to 12 engage in the set of primary supply sockets 2, the shutters shielding these sockets having been opened by the operating rods 19. When in this position the ground contacts 24 make contact with contact 24a fitted to the metal stationary housing to effect a grounding connection to a ground bar 24b. Grounding of the feeder circuits is then completed by closing the switching means to make a circuit from sockets 2 through extension plugs 10 to 12, primary supply plugs 6, the switching means, primary supply plugs 7, star point contacts'21 and ground contacts 24, 25 to the ground contacts on the housings.

If it is desired to effect testing of the feeder circuit the switching means in the movable housing is opened to break the ground circuitand handle 30 is moved counterclockwise to cause Ihooks 28 to engage pins 37 on thestationary housing and to cause the slots 29 to disengage from the-pins 29a on the movable housing. The movable housing can then be withdrawn leaving the device supported on the stationary housing as shown in FIG. 5. With the device in this position it will be seen that the extension plugs 10 to 12 effectively extend the sockets 2 further forward to the positions of sockets 16 to 18, and so improve the accessibility for testing purposes. I

i The interlock members 31 guard against the possibility of manual insertion of the device into the stationary housing, as the-ends 38 of the members 31 engage the side plates of the stationary housing and prevent contact of contacts 13 to with sockets 2 or 3. When the device is fitted onto the movable housing the sections 35 are engaged by the housing and are moved outwardly, so moving members 31 against their spring bias to cause ends 38 to be drawn inwardly so that fitting to 4 the stationary housingisunimpeded.

FIG. 6 shows that the device may also be used invetted so that the-extension plugs to, 12 engage the busbar sockets 3 in the stationary housing and allow these to be groundin a manner analogous to that already described. Once again the device is held on the movable housing by engagement of slots 29 with pins 29a. However, hooks 28'will not engage pins 37 on the stationary housing, and indeed such engagement is unnecessarysince there .is no need for retention of the grounding device on the stationary housing when the busbar sockets are being engaged. 3

What I claim is: I

l. A groundingand testing device for use in electrical switchgear having a stationary housing with two sets of primary supply sockets for feeder and busbar circuits respectively and a movable housing with two sets of primary supply plugs for connection to the sockets and connected to the contacts of switching means in the movable housing, the device comprising a carrier, a set of primary supply extension plugs mounted on the carrier for engaging at one end thereof a set of the primary supply sockets and at the other end thereof a first set of the primary supply plugs, a set of primary supply contacts on said carrier for engaging a second set of the primary supply plugs, ground contacts connected to the primary supply contacts, first locking means for locking theicarrier in position on the movable housing, and second locking means for locking the carrier in position on the stationary housing.

2. A device according to claim 1 in which the locking means are interconnected to that when one is fully engaged the other is disengaged.

3. A device according to claim 2 in which the locking means comprise a lever pivotally mounted between its ends on the carrier, a first end of the lever being formed with an arcuate slot for engaging with a pin on the movable housing and constituting the first locking means, and a second end of the lever being formed with a hook for engaging a pin on the stationary housing and constituting the second locking means.

4. A device according to claim 3 in which two of said levers are provided, one at each side of the carrier, the leversbeing joined for commonpivotal movement.

5. A device according to claim 1 in which interlock members are provided on the carrier for preventing engagement of the device with a stationary housing unless the device is already locked in position on a movable housing.

6. A device according to claim 5 in which there are two interlock members, one at each side of the carrier, and each comprises a lever pivoted to the carrier and spring biased to a position wherein a first end of the lever projects beyond the side of the carrier to prevent engagement with the stationary housing, the second end of the lever being shaped to be deflected when mounting the carrier on the movable housing to withdraw the first end of the lever from its projecting position. 

1. A grounding and testing device for use in electrical switchgear having a stationary housing with two sets of primary supply sockets foR feeder and busbar circuits respectively and a movable housing with two sets of primary supply plugs for connection to the sockets and connected to the contacts of switching means in the movable housing, the device comprising a carrier, a set of primary supply extension plugs mounted on the carrier for engaging at one end thereof a set of the primary supply sockets and at the other end thereof a first set of the primary supply plugs, a set of primary supply contacts on said carrier for engaging a second set of the primary supply plugs, ground contacts connected to the primary supply contacts, first locking means for locking the carrier in position on the movable housing, and second locking means for locking the carrier in position on the stationary housing.
 2. A device according to claim 1 in which the locking means are interconnected to that when one is fully engaged the other is disengaged.
 3. A device according to claim 2 in which the locking means comprise a lever pivotally mounted between its ends on the carrier, a first end of the lever being formed with an arcuate slot for engaging with a pin on the movable housing and constituting the first locking means, and a second end of the lever being formed with a hook for engaging a pin on the stationary housing and constituting the second locking means.
 4. A device according to claim 3 in which two of said levers are provided, one at each side of the carrier, the levers being joined for common pivotal movement.
 5. A device according to claim 1 in which interlock members are provided on the carrier for preventing engagement of the device with a stationary housing unless the device is already locked in position on a movable housing.
 6. A device according to claim 5 in which there are two interlock members, one at each side of the carrier, and each comprises a lever pivoted to the carrier and spring biased to a position wherein a first end of the lever projects beyond the side of the carrier to prevent engagement with the stationary housing, the second end of the lever being shaped to be deflected when mounting the carrier on the movable housing to withdraw the first end of the lever from its projecting position. 